A positive Tinel’s sign is a finding from a simple physical examination that helps medical professionals identify and locate problems within the body’s peripheral nervous system. The test is a diagnostic tool used when a patient reports symptoms like tingling, numbness, or pain in a limb, suggesting a possible issue with an underlying nerve. A positive result provides a physical indication that a nerve is irritated or damaged, which is a strong clue for diagnosing various conditions involving nerve compression or injury.
Understanding the Mechanics of the Tinel’s Test
The Tinel’s test involves lightly tapping or percussing the skin directly over a peripheral nerve suspected of irritation or compression. The clinician typically uses a finger or a small reflex hammer. The tapping location is highly specific, targeting areas where the nerve passes through a narrow anatomical space, such as a tunnel or groove.
A positive Tinel’s sign is determined by the patient’s subjective experience. Tapping the skin elicits a sudden, electrical, or tingling sensation, often described as “pins and needles” or paresthesia. This feeling radiates distally along the nerve’s path from the point of percussion, indicating a direct response of the irritated nerve fibers to the mechanical stimulus.
The Physiological Meaning of a Positive Result
The tingling sensation defining a positive Tinel’s sign results from hyperirritability in the nerve’s axon structure. When a nerve is stressed by compression or injury, the protective myelin sheath surrounding the fibers can become compromised. The mechanical stimulus of tapping causes these exposed or damaged fibers to generate an abnormal electrical impulse.
This positive sign primarily indicates that a nerve is entrapped or compressed by surrounding tissues, such as bone, ligament, or tendon. The ongoing pressure makes the nerve highly sensitive to external force, like the tap from the test.
However, a positive result can also signal nerve regeneration following an injury. As a damaged nerve heals, new, highly sensitive axons attempt to grow back along the nerve’s pathway. Tapping over the site of this new growth stimulates the fragile, newly formed axons, producing the radiating tingling sensation. Monitoring the location of the positive sign over time helps track the progress of nerve regrowth.
Specific Neuropathies Identified by the Tinel’s Sign
The Tinel’s sign is applied across various peripheral nerves, and the location of the positive finding helps pinpoint the specific condition. It is frequently used over the median nerve at the wrist to diagnose Carpal Tunnel Syndrome (CTS). Tapping directly on the palm side of the wrist crease, where the median nerve enters the narrow carpal tunnel, provokes the characteristic tingling.
A positive sign here causes the sensation to radiate into the thumb, index finger, middle finger, and the thumb-side half of the ring finger. This distribution confirms the median nerve is being compressed by inflammation or swelling within the carpal tunnel.
The sign is also used to evaluate the ulnar nerve, often called the “funny bone,” at the elbow. Tapping over the ulnar nerve as it passes through the cubital tunnel suggests Cubital Tunnel Syndrome. A positive result causes tingling to radiate into the little finger and the pinky-side half of the ring finger, confirming nerve irritation from compression.
The sign’s versatility extends to the lower extremity, aiding in the diagnosis of Tarsal Tunnel Syndrome. The clinician taps the posterior tibial nerve as it travels along the inside of the ankle, just above the heel. A positive finding causes tingling or numbness to radiate into the sole of the foot, consistent with compression of that nerve within the tarsal tunnel.